A fiber laser oscillator is constituted to have a chassis, an optical engine housed in the chassis substantially in a tightly sealed state, a control device for controlling the oscillation operation, and a cooling device. The optical engine is comprised of a plurality of fiber laser modules each having a semiconductor laser as a laser light source and a combiner for combining the laser lights respectively generated by the fiber laser modules. The laser light combined by the combiner is output to the exterior via a processed fiber.
Efficiency of laser oscillation by a semiconductor laser generally has some temperature dependency. It is thus necessary to retain a temperature of the optical engine that produces heat in accordance with laser light oscillation within a proper temperature range by cooling, so as to assure high oscillation efficiency steadily. The cooling device is provided for the purpose of proper temperature management of the optical engine. This cooling is carried out by inflow and circulation of cooling water of 24 degrees C. for instance through a coolant conduit (cooler pipe) arranged in the chassis.
In the meantime, if the quantity of water vapor contained in the air within the chassis exceeds a saturated water vapor quantity at the temperature of the cooling water (24 degrees C. for instance), condensation will occur on the surface of the cooler pipe, which gives rise to greater possibility for malfunction of electronic devices in the optical engines. It is therefore necessary to postpone injection of the cooling water into the cooler pipe until humidity of the air within the chassis and the air within the fiber laser module is sufficiently reduced by a dehumidifier device.
The Patent Literature 1 proposes a fiber laser oscillator comprised of such a dehumidifier device in a chassis, which is comprised of a dehumidifier device for supplying dried air (dry air with a low dew point) respectively to a plurality of LD modules in the chassis. In more detail, it proposes an example in which dry air with a low dew point obtained by dehumidifying is supplied at a rate of 1 L (1 dm3) per minute by a small pump, while it is also described to use a device for supplying purging air, which had been also installed in laser processing devices or such, which have been used in laser processing machines.